Dental Radiology Final Exam

ionization

the production of ions, the process of converting an atom into an ion, deals only with energy to overcome the electrostatic force that binds the electron to the nucleus, resulting in the formation of a positive atom and a dislodged negative electron

penumbra

fuzzy border of an object as imaged radiographically

filtration

the use of absorbing materials (ex. aluminum) for removing the low-energy x-rays from the primary beam

lead apron

a flexible lead shield used to protect the patients reproductive and blood forming tissues from scatter radiation

collimation

the restriction of the size and shape of the x-ray beam in order to reduce patient exposure

ALARA

a concept of radiation protection that states that all exposure to radiation must be kept to a minimum, or "as low as reasonably achievable

density

the overall darkness or blackness of an image

latent image

the pattern of stored energy on the exposed film; the invisible image produced when the film is exposed to x-rays and that remains invisible until the film is processed

latent period

the amount of time that lapses between exposure to ionizing radiation and the appearance of observable clinical signs

Compton scatter

one of the interactions of x-radiation with matter in which the x-ray photon collides with a loosely bound, outer shell electron and gives up part of its energy to eject the electron from its orbit. the x-ray photon loses energy and continues in a differe

intensifying screen

a device that transfers x-ray energy into visible light; the visible light in turn , exposes the screen film, these screens intensify the effect of x-rays on the film, with its use less radiation is required to expose screen film, and patient is exposed t

foreshortening

a term describing images of teeth that appear too short; it is a result of excessive vertical angulation

elongation

a term describing images of teeth that appear longer than the actual teeth; it is the result of insufficient vertical angulation

primary beam

the penetrating x-ray beam produced at the target of the anode and that exits the tube-head

radiation

a form of energy carried by waves or a stream of particles

general radiation

a form of radiation that occurs when speeding electrons slow down because of their interactions with the tungsten target in the anode - AKA- Bremstahlung or braking radiation

characteristic radiation

a form of radiation that occurs when a high speed electron dislodges an inner shell electron from an atom, causing excitation, or ionization of the atom

electromagnetic radiation

the propagation of wavelike energy through space or matter, the propagated energy is accompanied be electric and magnetic fields, thus the term electromagnetic. examples: cosmic rays, gamma rays, x-rays, ultraviolet rays, visible light, infrared light, ra

ionizing radiation

radiation capable of producing ions; includes particulate or electromagnetic radiation

particulate radiation

tiny particles of matter that possess mass, travel in straight lines, and also travel at high speeds

scatter radiation

a form of secondary radiation; results from x-ray beam that has been deflected from its path by the interaction with matter

secondary radiation

radiation created when the primary beam interacts with matter; it is less penetrating than primary radiaiton

contrast

how sharply dark and light areas are differentiated or separated on an image; the difference in the degrees of blackness (densities) between adjacent areas on a dental radio graph

scale of contrast

the range of useful densities seen on a dental image

long scale of contrast

a term describing an image with many densities, or many shades of gray; it results from the use of a higher kilo-voltage range

short scale of contrast

a term describing an image with only two densities, areas of black and white; it results from a lower kilo-voltage range

high contrast

a term describing an image with many very dark areas and very light areas and few shades of gray

low contrast

a term describing an image with many shades of gray and few areas of black and white

radiolucent

the portion of an image that is dark or black; this structure readily permits the passage of the x-ray beam and allows more x-rays to reach the receptor

radiopaque

the portion of an image that is light or white, this structure is one that resists the passage of the x-ray beam and limits the amount of x-rays that reach the receptor

kVp

the maximum of peak voltage that is used during an x-ray exposure. Low kVp=short scale=high contrast
High kVp=long scale=low contrast

wavelength

determines the energy and the penetrating power of radiation. Shorter wavelengths=more penetrating power
Longer wavelengths=less penetrating and more likely to be absorbed by matter

quality

is used to describe the mean energy or penetrating ability of the x-ray beam- the quality, or wavelength and energy of the x-ray beam is controlled by kilo-voltage

voltage

a measurement of force that refers to the potential difference between two electrical charges. Voltage= determines the speed of electrons that travel from the cathode to anode, When the voltage is increased- the speed of the electrons increases, the elect

volt

the unit of measurement used to describe the potential that drives an electrical current through a circuit

kilovolt

1 likovolt is = 1000 volts

kilo-voltage

can be adjusted according to the individual diagnostic needs of the patient. the use of 85 to 100 kV produces more penetrating x-rays with greater energy and shorter wavelengths, 65 to 70 kV produces less penetrating dental x-rays with less energy and lon

quantity

this of the x-ray beam refers to the number of x-rays produced in the x-ray machine

amperage

determines the amount of electrons passing through the cathode filament, an increase in he number of electrons available to travel from the cathode to the anode results in the production of an increased number of x-rays

ampere

the unit of measure used to describe the number of electrons or current flowing through the cathode filament

impulses

what exposure time is measured in, because x-rays are created in a series of bursts and pulses rather than in a continuous stream, 1 impulse occurs every 1/60 of a second, or 60 impulses occur in 1 second

milliamperage

this regulates the temperature of the cathode filament. if it is increased the temp of the cathode filament increases, and consequently the number of electrons produced increases. an increased number of electrons that strike the anode increases the number

7-15

the mA in dental radiology is what?

density

an increase in mA increases the overall ______ of a radio graph and results in a darker image.

exposure time

milliamperage and _______ are inversely related, when altering the mA, this must be adjusted to maintain diagnostic density of an image. increase mA-descrease___, decrase mA-increase____

contrast

milliamperage affects ________.

intensity

is described as the product of the quantity (# of x-ray photons) and quality (energy of each photon) per unit of area per unit of time exposure. it is affected by kVp, mA, Exposure time, and distance.

distance

the _________ traveled by the x-ray beam affects the intensity of the beam

target surface distance

the distance from the source of radiation to the patients skin

target object distance

the distance from the source of radiation to the tooth

target receptor distance

the distance from the source of radiation to the receptor

inverse square law

the intensity of radiation is inversely proportioned to the square of the distance from the source of radiation. "inversely proportional" means that as one variable increases, the other decreases.

Wilhelm Conrad Roentgen

This Bavarian physicist discovered the x-ray on November 8, 1895

velocity

the speed of a wave of electromagnetic radiation.

frequency

the number of wavelengths that pass at a given point in a certain amount of time. this and wavelength are inversely related, ____ increased= short wavelength, decreased ___= long wavelength.

aluminum disks

these can be added to the tube head in 0.5mm increments, the purpose is to filter out the longer wavelengths, low-energy x-rays from the x-ray beam. the low-energy longer wavelength x-rays are harmful to the patient and are not useful in diagnostic radiol

total filtration

dental x-ray machines operating at or below 70 kVp require a minimum of 1.5mm of aluminum filtration, machines operating above 70 kVp require a minimum of 2.5mm aluminum filtration.

circular collimator

when using a _____ _____, federal regulations require that the x-ray beam be collimated to a diameter of no more than 2.75 inches as it exits from the PID and reaches the patients skin.

inherent filtration

this is approximately 0.5-1.0mm of aluminum**
this does not meet regulated standards by state and federal law
**

maximum permissible dose

MPD- the maximum dose equivalent that a body is permitted to receive within a specific period, it is the dose of radiation that a body can endure with little or no injury.

5.0/rems/year = 0.05/Sv/year

maximum permissible dose for occupationally exposed persons

0.1/rem/year = 0.001/Sv/year

maximum permissible dose for non-occupationally exposed persons, or pregnant women who are occupationally exposed

MAD

maximum accumulated dose, this is the maximum dose of radiation that a person can be exposed to in a lifetime. formula=MAD=(N-(persons age in years)-18) X 5 rems/year,
MAD=(N-18)X 0.5 Sv/year

primary beam

the dental radiographer must always avoid the _______

6 feet

radiographer must maintain a distance of at least _____ from the x-ray tube head, or stand behind a protective barrier wall

90-135 degree

radiographer must position themselves at a _______ angle to the primary beam, for protection

tissue sensitivity

how sensitive certain body tissues are to radiation exposure

most sensitive tissues

reproductive, lymphoid, bone marrow

least sensitive tissues

nervous system, skeletal system, mature bone

law of B & T

the faster the reproductive rate of the cells and tissues, the more sensitive they are to radiation, the more specialized the cells and tissues are the less sensitive to radiation they are

period of injury

this occurs after the latent period, following exposure to radiation, can include a variety of cellular injuries

recovery period

the period during which cellular damage caused by radiation is followed by repair

lethal dose

LD- 50/30, kill 50% of the population in 30 days

coulombs/kg

old name was rotengen= measures x-ray exposure in air

gray

old name was rad= measures x-rays absorbed by tissues

sievert

old name was rem= measures effects (damage) on man

erythmea

redness, the first sign of exposure to radiation

alopecia

loss of hair, a common sign of radiation exposure

fixer solution

a chemical solution used in processing; removes the unexposed silver halide crystals and creates white or clear (radiopaque) areas on film

10 mins, 1.5 mins

fixer time for manual processing is ____, and _____ for automatic processors

developer solution

a chemical solution used in film processing that distinguishes between exposed and unexposed silver halide crystals and makes the latent image visible.

5 mins, 1.5 mins

developer time for manual processing is _____, and ____ for automatic processors

68, 80

the temperature for developer solution for manual processing is ____ degrees, and ______ degrees fro automatic processing

the bisecting technique

this is based on a geometric principle of bisecting a triangle, the angle formed by the long axis of the teeth and the film is bisected, and the x-ray beam is directed perpendicular to the bisecting line, (perpendicular means at a right angle to the film)

brown film or image

this is a processing error that is caused by insufficient fixing or washing

black marks

this is an error made during processing caused by nail pressure to film,or possibly light or saliva leaks through the film packets

cone cut

a clear unexposed area on a dental radiograph that occurs when the PID is misaligned and the x-ray beam is not centered over the film

coronoid process

what is the only mandibular landmark that appears on a maxillary periapical?

X-Y formation

where the nasal fossa intersects with the maxillary sinus, usually near the lateral incisor or canine

mandibular foramen

you will not see this on a periapical or intra-oral shots

enamel

the most radiopaque and most calcified substance in the body, followed by cementum, and dentin

filaments heat

1st step in the process of producing x-rays

electrons released

2nd step in the process of producing x-rays

electron cloud forms

3rd step in process of producing x-rays

4th step in process of producing x-rays

high voltage circuit activated to create speed of electrons

stopping of target

5th step in the process of producing x-rays

x-rays are the product

the final step in the process of producing x-rays

dupilcator

identical copy of an extra/intra oral radio graph, this requires the use of a film dupilcator, a light source that is commercially available from the manufacturers, it provides a diffused light source that evenly exposes the special duplicating film

kVp change problem formula

increase kVp by 15, and decrease exposure time by 1/2.

mA change problem formula

mA's old=mA's new
(old) mA X sec = mA X (new) sec

film speed change problem formula

with each change in speed, the exposure time needed halves, with each decrease in speed, the exposure time needed doubles. A_F film speeds A=slowest, F=fastest.

intensity change problem formula

(new) intensity = (old) distance
(old) intensity = (new) distance

exposure time change problem formula

(new) exposure time = (new) distance
(old) exposure time = (old) distance

film fog

blurry film- little bit of exposure to the whole film, possible causes= incorrect filter, improper safe-light, incorrect bulb, or incorrect distance

differences in direct and indirect exposure

direct exposure film is exposed by x-rays, and indirect exposure film is exposed by florescent light from intensifying screens

outer wrapping of film

plastic that protects film from light and moisture

lead foil

helps protect the x-ray from scatter radiation, it has a herringbone imprint on it so it can detect if film was exposed backwards

black paper of film

goes around the front and back of film and helps protect the film from light and moisture if there is a leak in the outer wrapper

film

to capture and make a permanent image, has an outer protective coating on front and back

emulsion

on the front and back of film, contains silver halide and bromide crystals

energizes

when x-rays hit the crystals it ____ them, where the x-rays are blocked the crystals did not get ____. when processed the crystals that are ____ are radiolucent, and the ones not _______ are wiped away from fixer, these are radiolucent.

plastic base

base of film packet

description of latent image production

once the film is exposed, the crystals that are energized (the ones holding the image by holding the energy), the films have been exposed but they have not been processed yet

faster

the larger the crystals the _____ the speed

definition

faster film is less crisp and has less _____

bitewings

used to show the crowns of teeth, alveolar crest, and the interproximal area- taken once a year

periapicals

used to obtain a view of the entire tooth and its periodontal supporting structures

occlusals

used to show large areas of the maxilla, mandible, or the floor of the mouth

panoramic

used to show large areas of the maxillary and mandibular arches with adjacent structures

lateral oblique mandible

used to view the mandible from the canine region posteriorly to the body and ramus

TMJ survey

reveals the relationship of the head of the mandibular condyle in relation to the glenoid fossa of the temporal bone

posteroanterior survey

revelas the entire skull in the posteroanterior plane; often used as a supplement to the lateral skull survey

cephalometric

lateral skull- used in orthodontics to measure the head

occlusal

3X 2 1/4" Size no. 4 film speed D; used to visualize a cross section of an area